Building a Complex Pulley System

In this project, I designed and built a three-pulley system to demonstrate mechanical advantage. The setup makes it easy to see how pulleys reduce the effort needed to lift a load, providing a simple yet effective way to understand the concept in action.

1. 3D Printer (PLA compatible)
2. Flashprint Application
3. PLA Filament
4. Fusion Application
5. 5mm width wooden sticks (length respectively 3 of 4cm, and 1 of 10cm)
6. Around 3.5mm wide string (length respectively 3 of around 60cm)
7. Hand Drill (5.5mm, 4mm, countersink drill bits)
8. 6 Screws 6x1-1/2"

You will be designing the pulley, the hook for hanging the pulley, and the size of the backboard in this step. An easy shortcut is also available, the files for the pulley and hook are downloadable below. In the following steps, numbered images are added based on the step number to better clarify the instructions.

Designing the Pulley

1. Open Fusion, and create a new file.
2. Create Sketch on plane x, and draw two circles with the same origin, respectively 10mm and 50mm width.
3. Extrude the donut part of the circle to 8mm height.
4. 
   
5. Create a sketch on plane x, and draw a circle with 6mm width.
6. Double click the circle, choose move/copy, and move the circle onto the vertically middle side of the donut.
7. Press Revolve, click the circle, click the axis, then click the outside belt of the circle, it should look like this. If it does, then the pulley is done. Next, we will move onto the process of making the hook.

1. On the same file, start a sketch on either plane, then draw a 65mm by 20mm rectangle. Do not click the finish sketch yet.

1. Under modify, click offset. Choose all the four corners of the rectangle, keep the length of the fillet at 5mm. It should look like this.
2. Draw approximately at the upper part of the rectangle a circle of 9mm, and at the lower part a circle of 6mm. Use the grids to help position the center of the circle in the middle of the width. Finish the sketch.
3. Pressing command, choose both the rectangle and the 6 mm circle, then extrude 2mm.
4. Select the body, press Command-C and Command-V, and drag the copied body 12mm to the right.
5. Re-open the visibility of the last sketch, which would be automatically turned off after extruding.
6. Choose the 5.5mm circle, extrude 12mm, and choose join instead of the default cut. The two rectangles should now be joined together.
7. Double click the body, choose save as mesh, and save the properties as seen below. After this is done, click OK and save it as “hook”, and select “save to my computer”. Save it to whichever folder preferred. Do the same for the body of the pulley, and save it as “pulley”.

In this part of the tutorial, we will go straight into printing with the Flashprint ready for use. If you haven’t downloaded Flashprint yet, refer to this link and download: https://www.flashforge.com/pages/software-flashprint?srsltid=AfmBOopSYc69kQbgz3otRu1l6r7WngU0piro7RjgUpC95tFcydHH1trr. Only initialization of the software is needed, as the steps will fully explain what is needed to do.

1. Drag either one of the hook or pulley files into the Flashprint page. The file should then appear on the screen.
2. For settings:
3. Go to “Move” and click “On Platform” and “Center”
4. Go to “Support” and choose autosupports. Make sure that the support type is the one with the parallel lines. Red lines should appear on the model.
5. Click “Back”, and on the left bottom side of the screen, choose the printer compatible with the one you own. In this case, I am using an Adventurer 5M Pro.
6. Click “Slice”, then go to the bottom right corner and click “Slice”.

1. For preparing to print:
2. Clicking the power button of the printer, turn it on.
3. FInd the “Hotspot” switch on the digital screen, and turn it on as well. The IP address will be needed later.
4. Go back to Flashprint, and connect the wifi of the computer to the hotspot of the printer.
5. Press the button circled in the image below, and select IP address. Fill in the IP address of the printer. The IP address should be found on the Hotspot page.
6. Press connect machine.
7. Your printer will appear on the screen. Choose the printer, and select “Connect”.
8. Input any filename preferred, and click OK. The model should now appear on the machine, and printing will start after the setup of the printer is complete. It should look like this.
9. The file should be printed now. The estimated time will appear on the printer, and you may take the finished product after the printing process has finished.
10. Print 4 of the “pulley” and 3 of the “hook”. This should take a while. To save time, you can print two or three together.

In this step, you will be putting the boards together to finish building the pulley system. I will show the dimensions of the wooden boards that I used, but it can also be scaled up or down based on needs. Some steps will need to be adjusted in this case but not much will be changed.

1. Prepare wooden boards according to the size below. The only thing to keep in mind when scaling up or down the boards is that the width needs to be the same. The thickness of the wooden board can be around 16-24mm.
2. Drill 3 4mm wide holes each in this side of the two smaller boards as seen below. The width difference can also be seen in the image. If the size of the board is scaled differently, try to keep the holes away from the sides, and keep them equal in difference in length.
3. Tip: If you have a clamp or anything that can hold the board, use the tool to help fix the boards in position. If not, get someone to help fix the position. It can be quite difficult to control the boards.
4. Now that you have six holes, 3 in each of the two boards, use the countersink drill to drill 3mm into each drill hole. This will make sure that the screws you put in will not be sticking out.（need to take a pic for this）
5. Take out the six screw 6x1-1/2". Using the screwdriver head of the drill, drill and six into the holes, which connects the two small boards and the back board.
6. What is finished will look like this.

1. Prepare the pieces of string, wooden sticks, and printed material.
2. Drill 5mm holes into these respective positions. These holes should be drilled on the top small board and the large back board. If the sizes of your boards are different, just adjust it roughly so that it looks proportionally the same.
3. In the hole in the big back board, push the 10cm wood stick so most of the stick is visible in the front. Put a pulley on the wooden stick in the front.
4. Tie knots bigger than the 5mm hole on one side of each of the three strings, it should look roughly like this.
5. Push the strings through the three holes on the top small board, it should look like this.
6. For each of the three pulleys and hooks left, push a 4cm wooden stick through like this.

Assemble the parts based on the instructions in the images. You can cut excess string after step 3.

Your done! This it what it will roughly look like.